Boiler top mounting arrangement for pressure relief valves



June 18, 1963 c. o. MYERS 3,0

BOILER TOP MOUNTING ARRANGEMENT FOR PRESSURE RELIEF VALVES Filed May 5, 1961 I comm-saw 14/ TA 1w: g 1

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United States Patent 3,094,281 BOILER TOP MOUNTING ARRANGEMENT FOR PRESSURE RELIEF VALVES Carl 0. Myers, 1155 N. High St., Columbus, Ohio Filed May 5, 1961, Ser- No. 108,082 3 Claims. (Cl. 231-63) This invention relates to closed hot water heating systems and more particularly is concerned with a novel boiler top mounting arrangement for-a pressure relief valve wherein the valve connection to the boiler prevents loss of system air through the valve.

It is well established that in closed hot water heating systems the water being heated in the boiler releases air which rises in the form of bubbles to gather at the top of the boiler. Modern systems are arranged to allow air bubbles to accumulate at the top of the boiler and include facilities for directing such accumulated air to a compression tank to act as an air cushion (for absorbing normal expansion of the system water during each heating cycle.

A description of a typical cycle of operation for such a system better illustrates the action of the system air. When the burner is operating and heat is applied to the boiler, air bubbles are released by the water in the boiler and the boiler water also expands to force water into the compression tank as system pressure increases. The water that enters the comparatively cool compression tank absorbs air from the air cushion at the top of the tank. When the thermostat turns off the fuel burner, the boiler water cools, system pressure is reduced and water having entrained air absorbed therein flows from the compression tank back to the boiler. The absorbed air in this returning water is again released in bubble form in the boiler with the bubbles rising to the top of the boiler. Any leak existing at the top of the boiler allows air to escape from the system during each heating cycle and thus progressively reduces the air cushion in the compression tank.

In such closed hot water heating systems, it is accepted and preferred practice to mount a pressure relief valve directly on top of the boiler. It has been determined, however, that in the prior art arrangements of this type, the air within the top of the boiler can and does leak past the valves seal face to provide a progressive reduction of the air cushion in the compression tank. Ultimately the air cushion is reduced to a point where normal water expansion occurring during each heating cycle cannot be accommodated without developing system pressures in excess of the relief valve setting.

Where air leakage through the pressure relief valve reduces the system air cushion to the point where the air cushion is unable to prevent an excessive rise of the system pressure, the relief valve will operate to discharge water from the boiler, thus reducing the total water content of the system. Then when the boiler cools, lack of pressure in the system permits a recession of the water in the radiation at the top of the system. Moreover, the more often a relief valve operates, the greater its tendency to leak becomes. This is particularly true as respects air leakage through the valve.

The principal object of the present invention is to provide a boiler top mounting arrangement for a pressure relief valve for preventing air leakage through the valve.

A more specific object of the invention is to provide such a mounting arrangement wherein a dip tube structure directly connects the pressure relief valve to the top of the boiler and projects into the boiler water to exclude system air from gaining access to the valve.

Other objects and advantages will become apparent during the course of the following description.

Patented June 18, 1963 in the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a diagrammatic elevational view of the pertinent portions of a closed hot water heating system embodying the present mounting arrangement for isolating system air from the pressure relief valve of the system;

FIG. 2 is a vertical sectional view through a typical pressure relief valve; and

FIG. 3 is an enlarged side elevational view illustrating a preferred dip tube fitting structure utilized for direct boiler top mounting of the pressure relief valve.

Referring now to the drawings, for purposes of illustrative disclosure, a closed hot water heating system is shown in FIG. 1 wherein the numeral 10 designates a hot water boiler having a water supply pipe 11 for circulating hot water to the system radiation, not shown. To provide for the thermal water expansion and to facilitate separation of air from water a pipe 12 is shown leading directly from the top of the boiler to the compression tank 14. A cold water fill line 15 with a hand operated fill valve or cook or a pressure reducing valve is shown connected to line 12.

During the operation of this system, air is freed from the water being heated in the boiler and rises in the form of bubbles to gather at the top of the boiler. This air is guided through the pipe 12 to the air cushion in the top of the compression tank. Closed hot water heating systems of this general type are equipped with a pressure relief valve 16 mounted in the top of the boiler 10 and the construction of one such typical valve is shown in FIG. 2. The valve 16 includes a casing 17 having an internally threaded bottom inlet opening 18 leading to a seal face 19 that is resiliently biased against an annular seat 20. When the system pressure exceeds a predetermined set value, the seal face is forced off its seat to allow the heating system to discharge through the valve.

In the past, where a pressure relief valve has been mounted at the top of the boiler, the system air gathering at the-top of the boiler has actually leaked through the valves seal face though such a minute discharge through the relief valve has gone unnoticed. Since this gathering of air at the top of the boiler occurs during each heating cycle, this air loss can accumulate to substantial proportions. Any air lost from such a closed system is, in effect, lost from the air cushion in the comp-ression tank 1 4 and causes a proportionate reduction in its cushioning effect leading to the development of excessive system pressures which in turn must be relieved by discharge through the pressure relief valve.

In accordance with the present invention a novel boiler top mounting arrangement, indicated generally at 21, is provided for the pressure relief valve 16 and employs a dip tube connection projecting into the boiler water to allow the boiler water to act as a seal for excluding system air from gaining access to the valves seal face and thereby prevents loss of system air due to leakage through the valve. In FIG. 1, air bubbles rising to the top of the boiler, merge forming a heavily air laden layer of water 22A at the top of the boiler. Normally, bubble laden water does not remain beneath the level indicated by the line 22. Thus the level designated by line 22 may be considered the effective lower limit of the bubble laden layer, or in other words, the water level in the boiler, and to prevent air from entering the main radiation supply line, the extension 11E normally provided in closed type hot water heating systems must project below the level 22. As is well known, the extension 11E enables the air laden water to be trapped in the top of the boiler and thus avoids the problems that arise when air is permitted to enter the main radiation supply line of the system.

The dip tube structure 21 is shown projecting to a point beneath this level to insure that air bubbles are permanently excluded from the region of the valve seal face. In the preferred constructional embodiment illustrated herein, the top of the boiler is provided with an internally threaded separate opening for receiving the dip tube mounting structure 21.

The clip tube structure is best shown in FIG. 3 and utilizes a tubular fitting 23 having external threads 23E on its lower end for sealing engagement with the threaded opening in the boiler 10, and having internal threads 231 at its upper end for sealing engagement with a pipe stub 24 which is in turn connected directly into the bottom opening 18 of the relief valve. A section 25 of tubing, which may be of steel, copper, or other suitable material, is rolled into the lower end of the fitting and is permanently fixed therein by pressing, soldering, brazing or equivalent procedures.

It will be apparent that the present boiler top mounting arrangement for a pressure relief valve is in general, useful in any closed hot water heating system wherein air bubbles are collected .at the top of the boiler and wherein a compression tank is arranged to provide an air cushion for accommodating thermal expansion of the system water.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title '35, of the US. Code and that the claims should be construed as broadly as prior art will permit.

I claim:

1. In a closed hot water heating system, in combination, a boiler, said boiler being able to collect bubble laden Water to define a water level adjacent but spaced beneath the top of the boiler, pipe means exiting from the top of said boiler and adapted to supply hot water to circulate through said system, said pipe means having an inlet in the boiler and extending below the water level therein, a compression tank providing an air cushion for thermal expansion of system water, pipe means exiting from the boiler at a location above said reference level for transferring air bubbles collecting in the top of the boiler to the air cushion in said compression tank, a pressure relief valve having a bottom inlet opening communicating with an internal seal face thereof, said seal face being arranged to control fluid discharge from said system through said valve, and dip tube mounting structure disposed in sealed relation in a separate opening in the top of said boiler and having its upper end connected directly into the opening in said valve and having its lower end projecting into said boiler to a point beneath the said water level therein to subject the said seal face to existing system pressure while excluding air of said system from contact and hence possible leakage through said seal face.

2. In a closed hot water heating system, in combination, a boiler, said boiler being able to collect bubble laden water to define a water level adjacent but spaced beneath the top of the boiler, pipe means exiting from the top of said boiler and adapted to supply hot water to circulate through said system, said pipe means having an extension projecting into the boiler to extend below the water level therein, a compression tank providing an air cushion for thermal expansion of system water, pipe means exiting from the boiler at a location above said reference level for transferring air bubbles collecting in the top of the boiler to the air cushion in said compression tank, a pressure relief valve having a bottom inlet opening communicating with an internal seal face thereof, said seal face being arranged to control fluid discharge from said system through said valve, and dip tube mounting structure disposed in sealed relation in a separate opening in the top of said boiler and having its upper end connected directly into the opening in said valve and having its lower end projecting into said boiler to a point beneath the said water level therein to subject the said seal face to existing system pressure while excluding air of said system from contact and hence possible leakage through said seal face.

3. An arrangement according to claim 1 wherein said separate opening in the top of said boiler has internal threading defining the same and said dip tube structure includes a tubular fitting having its upper end connected directly into the inlet opening of the valve and having its lower end provided with external threading for direct sealing threaded engagement in said separate boiler top opening and a length of tubing having its upper end secured Within said fitting and having its lower end projecting into the boiler and extending beneath the Water level therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,315,824 Sweeny Apr. 6, 1943 2,396,653 Hermanny Mar. 19, 1946 2,695,753 Kirk Nov. 30, 1954 2,699,760 Tidd Jan. 18, 1955 

1. IN A CLOSED HOT WATER HEATING SYSTEM, IN COMBINATION, A BOILER, SAID BOILER BEING ABLE TO COLLECT BUBBLE LADEN WATER TO DEFINE A WATER LEVEL ADJACENT BUT SPACED BENEATH THE TOP OF THE BOILER, PIPE MEANS EXITING FROM THE TOP OF SAID BOILER AND ADAPTED TO SUPPLY HOT WATER TO CIRCULATE THROUGH SAID SYSTEM, SAID PIPE MEANS HAVING AN INLET IN THE BOILER AND EXTENDING BELOW THE WATER LEVEL THEREIN, A COMPRESSION TANK PROVIDING AN AIR CUSHION FOR THERMAL EXPANSION OF SYSTEM WATER, PIPE MEANS EXITING FROM THE BOILER AT A LOCATION ABOVE SAID REFERENCE LEVEL FOR TRANSFERRING AIR BUBBLES COLLECTING IN THE TOP OF THE BOILER TO THE AIR CUSHION IN SAID COMPRESSION TANK, A PRESSURE RELIEF VALVE HAVING A BOTTOM INLET OPENING COMMUNICATING WITH AN INTERNAL SEAL FACE THEREOF, SAID SEAL FACE BEING ARRANGED TO CONTROL FLUID DISCHARGE FROM SAID SYSTEM THROUGH SAID VALVE, AND DIP TUBE MOUNTING STRUCTURE DISPOSED IN SEALED RELATION IN A SEPARATE OPENING IN THE TOP OF SAID BOILER AND HAVING ITS UPPER END CONNECTED DIRECTLY INTO THE OPENING IN SAID VALVE AND HAVING ITS LOWER END PROJECTING INTO SAID BOILER TO A POINT BENEATH THE SAID WATER LEVEL THEREIN TO SUBJECT THE SAID SEAL FACE TO EXISTING SYSTEM PRESSURE WHILE EXCLUDING AIR OF SAID SYSTEM FROM CONTACT AND HENCE POSSIBLE LEAKAGE THROUGH SAID SEAL FACE. 